The White House said it has not confirmed the authenticity of the video, according to the Associated Press.

White House National Security Council spokeswoman Caitlin Hayden told the Associated Press the administration has seen the video. The intelligence community is working as quickly as possible to determine if it is authentic, Hayden reportedly said.

"If genuine, we are appalled by the brutal murder of an innocent American journalist and we express our deepest condolences to his family and friends," Hayden said in a statement.

Blake Hounshell, the deputy editor of POLITICO magazine, apparently broke the news of the beheading video on Twitter.

"Yikes: ISIS claims to have executed American freelance journalist James Foley; threatening to kill Steven Sotloff next," he tweeted at 1:45 p.m. in a reference to the video.

He later tweeted that he watched the video. "Mistake," he wrote.

Foley has been missing since 2012, when he was last seen in northwest Syria,according to a "Find James Foley" Twitter account. Account officials sent a tweet at 2:16 p.m. asking Foley supporters to be "patient until we have more information."

Foley is a freelance journalist from Rochester, New Hampshire, according to the Associated Press. His parents live in New Hampshire, according to a 2013 Guardian report.

The high-definition video, which started with footage of President Obama and had a mic on the victim during the beheading, was posted on YouTube for more than an hour before it was taken down. YouTube cited a violation of its policy on violence.

Word of the news and graphic video caused a strong reaction on Twitter. Many users asked others to not search for the video, watch the video or post stills from the video online.

The end of the video reportedly showed American journalist Steven Sotloff alive. The narration tells Obama Sotloff's life "depends on your next deicison," according to USA Today.

Sotloff has worked for TIME, The National Interest and Media Line and has been missing since the middle of last year, according to the Wire. He hasn't tweeted since Aug. 3, 2013.